This invention relates to the graduated rule commonly used by draftsmen, engineers and architects to lay off, or measure distances and to establish linear proportionalities for representation on a technical drawing.
Currently in widespread use are instruments which contain either the standard series of architect's scales, the engineer's scales or special scales such as metric. A disadvantage of these devices is that two or more separate units are required for most applications. An additional disadvantage is that these devices have the graduations unprotected and subject to direct contact with both drafting instruments and the working surface of the drawing, which can cause the abrading away of the graduations. Furthermore, the user must physically select the desired scale and maintain its proper orientation to the working surface at all times. Thus, a substantial likelihood exists for inadvertantly using the incorrect scale. Also, the abrading away of graduations and numerals shortens the useable life of these devices.
It is the object of this invention to provide a measuring-scale instruments which overcomes the disadvantages of scales currently in use and which offers distinct efficiencies to the user-technician.